A known rotary electrical machine such as a generator motor mounted at a hybrid vehicle, an electric vehicle, or the like has a magnet inner rotor type in which a stator having a coil is arranged at an outer peripheral side while a rotor having a magnet is arranged at an inner peripheral side. According to the stator in the aforementioned rotary electrical machine, a stator core is formed by a lamination of a laminated material that is obtained by an annular punching of electrical steel and the like (i.e., annular cores). Because of a low yield rate of the annular-shaped laminated material, the stator core formed by a lamination of the laminated material that is divided in a circumferential direction at an even center angle (i.e., divided cores) may be commonly used. The multiple divided cores are integrally fixed to an inner periphery of a cylindrical stator holder by means of an integration technique such as a press-fitting and a shrink-fitting. According to the integration technique, the divided cores and the stator holder are manufactured individually so that an inner diameter of the stator holder is slightly smaller than an outer diameter of each of the divided cores. In case of press-fitting, the divided cores are forcibly pressed against the stator holder by an application of an external force so that the divided cores and the stator holder are integrally formed or molded. In case of shrink-fitting, the stator holder is heated and expanded. Then, after the stator holder accommodates the divided cores, the stator holder is cooled to contract, thereby integrally forming the divided cores and the stator core.
JP2008-193806A discloses an example of an electric motor constituted by a stator. According to the motor disclosed in JP2008-193806A, multiple divided cores (i.e., divided stators) are press-fitted to an inner peripheral surface of a cylindrical-shaped stator holder to thereby obtain the stator. A bending portion is formed at one end of the stator holder so as to bend into an inner peripheral direction. As a result, a torsional strength of the stator holder improves, which leads to a reduction of the number of components. In addition, a vibration noise caused by a decrease of rigidity of the motor is restrained.
At a time of the press-fitting or the shrink-fitting for integrally forming or molding the stator holder and the divided cores as disclosed in JP2008-193806A, a deformation of the stator holder may occur. Thus, according to the stator constituted by the divided cores, a position of a rotational axis may be inaccurate compared to the stator constituted by the annular cores. In a case where the rotational axis of the stator holder (the stator) and a rotational axis of a case of the rotary electrical machine do not mach each other when the stator is assembled on the case, a performance of the rotary electrical machine decreases. As a common means or method to specify a positional relationship or to match rotational axes of two members, which are not limited to the case and the stator, a positioning pin and a positioning bore may be used. That is, the positioning pin is provided at one of the two members while the positioning bore is provided at the other of the two members. The poisoning pin is fitted to the positioning bore to thereby specify the positional relationship of the two members.
However, a process to provide the positioning pin or the positioning bore at the stator holder should be performed after the deformation of the stator holder upon integral molding of the divided cores at the stator holder. That is, the process proceeds from a component manufacturing process to an assembly process, and then returns to the component manufacturing process. As a result, the process shifts back and forth by moving or transferring the stator, an extension of lead time, and a complicated process control in addition to reprocessing of the stator holder may occur.
A need thus exists for a stator assembly structure and method of a rotary electrical machine which is not susceptible to the drawback mentioned above.